Using Potentiometric Electrodes Based on Nonselective Polymeric Membranes as Potential Universal Detectors for Ion Chromatography: Investigating an Original Research Problem from an Inquiry-Based-Learning Perspective

Abstract

Because traditional laboratory practices in advanced chemistry education are being replaced by inquirybased approaches, we present herein a new laboratory activity based on a small research project that was designed and executed by students. The laboratory project aims at answering a well-defined research question: how far can potentiometric electrodes based on nonselective polymeric membranes be used as universal detectors in ion chromatography (IC)? Hence, the experiments were designed and conducted to explore the analytical performances of potentiometric electrodes based on different commercial membranes that are typically used in electrodialysis. The nonselective behavior shown by the electrodes permits a critical evaluation of their further implementation as a universal detector of anions in regular IC. Thus, the students were able to integrate a nonselective potentiometric sensor to analyze several anions in flow mode, mimicking the signal that is to be obtained using such electrodes as an IC detector. The proposed practice covers different pedagogical purposes: (i) to develop competence toward "thinking like a scientist" through reflective teaching; (ii) to promote argumentation skills and critical decision making; (iii) to improve students' research-planning and experimental-design skills; (iv) to refresh conceptual knowledge about analytical detectors, which typically goes unnoticed in laboratory practices; and (v) to reinforce students' knowledge about the basis of potentiometry. Furthermore, the present document may serve as an easy guide to develop other laboratory practices based on potentiometric sensors.

Ion‐Selective Sensors Based on Laser‐Induced Graphene for Evaluating Human Hydration Levels Using Urine Samples

“…The LIG electrodes were fabricated by a one-step process of lasing a polyimide sheet (0.125 mm thick) with a CO 2 laser (see the Experimental Section and Figure 1). Such CO 2 lasers produce infrared light that heats polyimide and converts sp 3 hybridized carbon into sp 2 -hybridized carbon, thus converting polyimide to graphene. [27] Lasing parameters (speed, power, and frequency) were tuned to obtain graphene while preventing charring or burning of the polyimide, which can create a less conductive amorphous carbon structure.…”

“…Solid‐state ISEs contain no filling solution between the ion‐selective membrane and the underlying electrode, and consequently do not exhibit the issues associated with ionic solution loss. Such ISEs have therefore been implemented in a wide variety of applications including in situ water quality analysis, [ 3 ] electrolyte sensing in sweat, [ 4 ] and fertilizer monitoring in soils. [ 5 ] However, solid‐state ISEs are often prone to large signal drift, which may be caused by the formation of an aqueous layer between the ion‐selective membrane and the electrode.…”

“…A recently developed, less complex, alternative strategy to graphene circuit formation is through the use of laser induced graphene (LIG). LIG is created by lasing, generally with a benchtop CO 2 or UV laser, carbon-based materials such as polyimide to convert sp 3 -hybridized carbon into sp 2 -hybridized carbon found in graphene. [5,20] This lasing process combines graphene synthesis, patterning, and annealing into one step that can be performed outside of a cleanroom at ambient conditions.…”

Wearable Potentiometric Sensors for Medical Applications

“…The difference between this potential and that provided by the reference electrode leads to the potentiometric readout, i.e., EMF of the electrochemical cell (Figure 1a). Besides this, the concentration dependence of the potentiometric signal with the activity of the primary ion is described by the Nernst equation, and the plot of the EMF versus logarithmic activity provides per se the calibration graph of the ISE (Figure 1b) [3], which is employed to detect unknown ion concentrations in (aqueous) samples.…”

Autonomous Titration for Chemistry Classrooms: Preparing Students for Digitized Chemistry Laboratories

“…Inquiry-based practices are emerging as an alternative approach to conventional pedagogical methods to teach laboratory practice. [25][26][27][28] As a matter of fact, it has been demonstrated that inquiry-based learning with platforms such as RoboGen offers great opportunities to teach multidisciplinary skills. 29,30 NMRviewers designed with Matlab have been introduced to promote complex data analyses and modeling, 31 and 3D printing has recently been introduced to classrooms to prepare intuitive visualizations of the physical and chemical properties of the elements in the periodic table.…”